Ultrasonic examination is a non-destructive material testing procedure for investigating components made from sound-conducting materials such as metal, plastics, ceramic material or concrete, for internal and external faults and defects and inhomogeneities of all types, in particular, cracks, slag inclusions, cavities, etc.
As a result of the simple and universal applicability coupled with the fact that test personnel are not exposed to any radiation burden, ultrasonic examination methods are one of the most commonly used non-destructive material testing methods.
Using ultrasonic testing methods, for example, large forged parts such as wheel disks, shafts or hollow shafts which are subject to large loads in operation are tested with ultrasound, possibly after manufacturing and possibly in a relatively uncontoured state. If defects are found with the ultrasonic testing method, a decision can be made, based on the defect discovered, whether the tested component will be put to use or not.
For the recognition and better characterization of defects, the SAFT method (Synthetic Aperture Focusing Technique) is sometimes used. With in-phase addition of the measured ultrasonic signals, for each point in the volume of the component to be examined, a localized defect indication is obtained. In a variant of the SAFT method, the FT-SAFT method, signal analysis is carried out for faster calculation in the frequency range.
However, a disadvantage of the conventional SAFT method lies therein that no information is thereby obtained concerning the orientation or alignment of relatively small defects within the component, which can be significant for the assessment of whether a component will be used. The orientation of an existing defect can have varying significance depending on the specific loading and geometry of an individual component. If the component is, for example, a wheel disk, radially oriented defects within the component are problematic since tangential tensional forces promote the growth of the defect or crack. Tangentially oriented defects or cracks, on the other hand, can be more readily tolerated in the component.